In a semiconductor manufacturing process, in order to promote a yield ratio, an inspection process is set in various steps during the semiconductor manufacturing process, and particles on a semiconductor substrate, defects in a formed pattern, etc. are inspected. In the semiconductor manufacturing process, fine particles on the semiconductor substrate contribute to an insulation failure of wiring and a short circuit of wiring. Along with the progress of miniaturization of patterns on semiconductor devices, minute particles on a semiconductor substrate contribute to an insulation failure of a capacitor, breakage of a gate oxide film, etc. As miniaturization of the patterns on the semiconductor devices are progressed, smaller particles or smaller defects may contribute to a failure of semiconductor devices. Therefore, an inspection system capable of detecting smaller particles and defects (they can be expressed as “defect” in some cases) on the semiconductor substrate is required.
As a technique for detecting this kind of defects on a substrate, there is known a method in which a semiconductor substrate is irradiated with laser light to detect scattering light from a particle which adheres to the semiconductor substrate or from a defect formed on the pattern. In the method, comparing an image obtained by laser irradiation with an image obtained immediately prior to the image obtained by the laser irradiation makes it possible to eliminate a false report caused by a pattern, thereby enabling a particle and a defect inspection with high sensitivity and high reliability. In addition, as the technique for inspecting a defect, there is known a method in which a wafer is irradiated with coherent light, light emitted from a repetition pattern on the wafer is removed by a spatial filter, and scattering light from a defect which does not have repetition is emphasized to be detected. Note that Patent Documents 1 to 4 are cited as prior art.